10w vs 15w oil (Australia)

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Hi new to the forum... I have done a search and could not find much on the subject, but I am sure it has been discussed before. I am from Melbourne Australia and have a 5.7 LS1 V8 GM powered vehicle, it has always been dealer serviced using 10w40 Valvoline (a bulk delivery variant the dealers use). I have just decided to use a local workshop, more convenient location, and I asked what oil they put in it, they said 15w40 Castrol Magnatec Professional, (once again a bulk delivery variant the workshops use), I am a little concerned that the 15w may be a tad thick at start up, seeing the trend these days seems to be heading towards 0w and 5w oils, the climate here is roughly from 2 degrees C (36F) in the coldest winter to maybe 41C (105F) in our hotest summer. What are your thoughts on the 15W or should I go back to the 10w which I would have to supply to the workshop as they only carry 0w40 5w40 10w30 15w40 and 20w50 weights. Appreciate your thoughts.
 

Drewie

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 Originally Posted By: Throckmorton
Is the 15W a synthetic oil?
No it is a Synthetic Fortifield oil I guess a Semi Synthetic, the reason I asked the original question is that it has been running the 10w40 oil for the past 8 years and was a bit surprised when they said they had put a 15w40 in it.
 
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Rest assured both 10W/15W-40 are decent choices for your climate as far as conventional oil is concerned. If you're going the synthetic route, 0W/5W-40 would be fine as well. \:\!
 
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15W-40's, or the 15W (winter rating part) are rated at -20C for the Cold Cranking viscosity. You'd be ok down to that temperature, although cranking would be a little sluggish in that cold temps. If the temperature doesn't go below 0C (freezing) you're not even coming close to having a worry about the cold flow properties of a 15W rated oil.
 
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The oil you seem to refer to must be Valvoline 15w40 Engine Armour. Very good oil, well priced. Its description makes me think it contains synthetic Ester to compete with the Magnatec. Only how it comes in 5w30, and 10w40 as well. Using it in 1986 Corolla with excellent results.
 

Drewie

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 Originally Posted By: vxcalais
The oil you seem to refer to must be Valvoline 15w40 Engine Armour. Very good oil, well priced. Its description makes me think it contains synthetic Ester to compete with the Magnatec. Only how it comes in 5w30, and 10w40 as well. Using it in 1986 Corolla with excellent results.
What the workshop have used is Castrol Magnatec Professional 15w40, a bulk delivery workshop oil, I guess similiar to the 10w40 Magnatec you can buy from the retail outlets, except one is 10w the other 15w. Seems ok so far it was just that the Holden Dealership had been using a 10w40 Valvoline bulk delivery oil called 10w40 Valvoline Pro-Blend, which incidently has changed names to professional as well. I was just a bit surprised the new local workshop had gone for the 15w40 grade, as others have said in our temps it should be ok. I was mainly asking if there was much of a difference between 10w40 and 15w40.
 

Drewie

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 Originally Posted By: crinkles
i wouldn't sweat the difference. Is there a reason you are running 40 wt in stead of a 10w-30?
Just seems to be what the dealers are using here. There seems to be a leaning to the thicker oils here in Australia, a lot of the guys here with V8's are running 10w50 semi synth and 10w60 full synth oils, I think they like the thicker film strength at operating temp. 40 weight seemed like a good compromise, I was more concerned with the 10w vs 15w. The smaller 4 cylinder cars here seem to run a bit lighter, daughter has a 2006 Mazda 3 and the Mazda dealer runs a 5w40 full synthetic Castrol in that.
 
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 Originally Posted By: Drewie
 Originally Posted By: crinkles
i wouldn't sweat the difference. Is there a reason you are running 40 wt in stead of a 10w-30?
Just seems to be what the dealers are using here. There seems to be a leaning to the thicker oils here in Australia, a lot of the guys here with V8's are running 10w50 semi synth and 10w60 full synth oils, I think they like the thicker film strength at operating temp. 40 weight seemed like a good compromise, I was more concerned with the 10w vs 15w. The smaller 4 cylinder cars here seem to run a bit lighter, daughter has a 2006 Mazda 3 and the Mazda dealer runs a 5w40 full synthetic Castrol in that.
I used Amsoil 5w30 for both my Territory and 380, for your Commodore, probably AMO 10w40 with added ZINC formula would be good.
 
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 Originally Posted By: Drewie
 Originally Posted By: vxcalais
The oil you seem to refer to must be Valvoline 15w40 Engine Armour. Very good oil, well priced. Its description makes me think it contains synthetic Ester to compete with the Magnatec. Only how it comes in 5w30, and 10w40 as well. Using it in 1986 Corolla with excellent results.
What the workshop have used is Castrol Magnatec Professional 15w40, a bulk delivery workshop oil, I guess similiar to the 10w40 Magnatec you can buy from the retail outlets, except one is 10w the other 15w. Seems ok so far it was just that the Holden Dealership had been using a 10w40 Valvoline bulk delivery oil called 10w40 Valvoline Pro-Blend, which incidently has changed names to professional as well. I was just a bit surprised the new local workshop had gone for the 15w40 grade, as others have said in our temps it should be ok. I was mainly asking if there was much of a difference between 10w40 and 15w40.
Ahh ok. Its usually Valvoline who refer to their oils as Synthetic fortified. 10w 15w barely no difference. Same with 10w50 and 15w50 i have noticed no difference. 20w50 i can tell the engine has to yank it a bit when cold. Winter the 5w40 definately has its benefits here in Melbourne, the frosty mornings are a shocker. We had a few 0 here few weeks ago. The nights have been bad and its the first time i have used a 5w40 oil as thin and Shell Helix Ultra and im loving the start ups hehe. Not sure how she'll go in the summer though. A good 15w40 to look at is Penrite Sin 15w40. Use it all year round.
 
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 Originally Posted By: CATERHAM
Just curious,but what is specified in you owners manual for your LS1 GM V8? I'd buck the heavy oil biase and go with a 0W-30 or 5W-30 synthetic.
I too find this very interesting that they use and suggest a heavier oil than 5w-30. I have an 04 GTO (built in Aus by Holden) with the 5.7L LS1 and the owner's manual specifically warns againts not using heavier oil's. Just curious to why the difference for down there versus here in the US. This is from my OM. "SAE 5W-30 As shown in the viscosity chart, SAE 5W-30 is best for your vehicle. However, if it is going to be 0°F (–18°C) or above and SAE 5W-30 is not available, you may use SAE 10W-30. These numbers on an oil container show its viscosity, or thickness. Do not use other viscosity oils such as SAE 20W-50." And then it mentions it again "DO NOT USE SAE 10W-40, SAE 20W-50, OR ANY OTHER VISCOSITY GRADE OIL NOT RECOMMENDED"
 

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 Originally Posted By: ABomb369
 Originally Posted By: CATERHAM
Just curious,but what is specified in you owners manual for your LS1 GM V8? I'd buck the heavy oil biase and go with a 0W-30 or 5W-30 synthetic.
I too find this very interesting that they use and suggest a heavier oil than 5w-30. I have an 04 GTO (built in Aus by Holden) with the 5.7L LS1 and the owner's manual specifically warns againts not using heavier oil's. Just curious to why the difference for down there versus here in the US. This is from my OM. "SAE 5W-30 As shown in the viscosity chart, SAE 5W-30 is best for your vehicle. However, if it is going to be 0°F (–18°C) or above and SAE 5W-30 is not available, you may use SAE 10W-30. These numbers on an oil container show its viscosity, or thickness. Do not use other viscosity oils such as SAE 20W-50." And then it mentions it again "DO NOT USE SAE 10W-40, SAE 20W-50, OR ANY OTHER VISCOSITY GRADE OIL NOT RECOMMENDED"
The difference? No CAFE in Australia.
 
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 Originally Posted By: OVERK1LL
 Originally Posted By: ABomb369
 Originally Posted By: CATERHAM
Just curious,but what is specified in you owners manual for your LS1 GM V8? I'd buck the heavy oil biase and go with a 0W-30 or 5W-30 synthetic.
I too find this very interesting that they use and suggest a heavier oil than 5w-30. I have an 04 GTO (built in Aus by Holden) with the 5.7L LS1 and the owner's manual specifically warns againts not using heavier oil's. Just curious to why the difference for down there versus here in the US. This is from my OM. "SAE 5W-30 As shown in the viscosity chart, SAE 5W-30 is best for your vehicle. However, if it is going to be 0°F (–18°C) or above and SAE 5W-30 is not available, you may use SAE 10W-30. These numbers on an oil container show its viscosity, or thickness. Do not use other viscosity oils such as SAE 20W-50." And then it mentions it again "DO NOT USE SAE 10W-40, SAE 20W-50, OR ANY OTHER VISCOSITY GRADE OIL NOT RECOMMENDED"
The difference? No CAFE in Australia.
+1 if i were to run a 40 wt in it, i'd run a 0w-40... but, i'd rather run a synthetic 10w-30.
 

Drewie

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 Originally Posted By: ABomb369
 Originally Posted By: CATERHAM
Just curious,but what is specified in you owners manual for your LS1 GM V8? I'd buck the heavy oil biase and go with a 0W-30 or 5W-30 synthetic.
I too find this very interesting that they use and suggest a heavier oil than 5w-30. I have an 04 GTO (built in Aus by Holden) with the 5.7L LS1 and the owner's manual specifically warns againts not using heavier oil's. Just curious to why the difference for down there versus here in the US. This is from my OM. "SAE 5W-30 As shown in the viscosity chart, SAE 5W-30 is best for your vehicle. However, if it is going to be 0°F (–18°C) or above and SAE 5W-30 is not available, you may use SAE 10W-30. These numbers on an oil container show its viscosity, or thickness. Do not use other viscosity oils such as SAE 20W-50." And then it mentions it again "DO NOT USE SAE 10W-40, SAE 20W-50, OR ANY OTHER VISCOSITY GRADE OIL NOT RECOMMENDED"
Just had a read through my Holden manual, and it says the following for the 5.7 LS1 engine. This was printed back in 2001/2002 prior to SL an SM specs, it is the same specs for the '03 '04 etc cars. The dealers seem to go for the 10w40 weight. 'For optimum fuel economy use 10w30 ILSAC GF2 engine oil, If this oil is unavailable, use SG, SH or SJ engine oil, with a viscosity of 20w50 or 15w40'
 
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